Acute renal failure is a major contributing cause of death in patients in the intensive care unit partly due to the lack of a simple, rapid method of assessing kidney function. It would therefore be extremely useful if a direct measurement of renal function could be performed at regular intervals so that the neeed for any medical or surgical intervention could be identified before any significant damage occurred to the kidneys or other organs due to renal failure. We propose to develop a practical, cost effective instrument and protocol to provide the renal blood flow (RBF) data necessary to monitor renal condition and predict possible failure in ICU patients. The proposed solid state, nuclear detection system and accompanying nuclear medical protocols should fulfill this need. By the end of the Phase I program, the technology will have been sufficiently developed and tested to clearly demonstrate the feasibility of measuring renal blood flow in the ICU. The development of this new monitoring capability will lead to an important advancement in the field of renal function analysis as well as the creation of a potentially successful technical product.